Shaping signals in single current telegraph circuits



G. G. uen-Vr 2,128,680 SHAPING SIGNALS IN SINGLE CURRENT TELEGRAPHCIRCUITS4 I' Filed Julyv 1.3. 1936 Aug. 30, 1938.

l i v .B www@ jmfrm/ Patented Aug. 30, 1938 UNITED STATE SHAPING SIGNALSIN SINGLE CURRENT TELEGRAPH CIRCUITS George G. Light, Kew Gardens, N.Y., assigner to The Western 'Union Telegraph Company, New York, N. Y., acorporation of rNew York Application my is, 1936, serial No. 90,397

2 Claims.

This invention relates to a method of shaping the signals transmitted atvarious points in a single current circuit so that all of the signalsreceived at one end of the circuit or at a repeating l station shallproduce the same effect upon the receiving or repeating instrument,

Each point of transmission in a single current circuit represents eitheran operating station or cut-in facilities at a repeating station. Theoperating stations may be located at various distances from therepeating station, some closely adjacent and others many miles away. Theconductor connecting the stations with the repeater may embody a cable,an open wire or a combination of cable and open wire conductors.Opposite polarities of battery or generator may be applied at each endof the circuit or a battery may be applied at one end of the circuitwith the other end connected to ground.

In order to insure that signals sent from any particular operatingstation will be repeated without bias, the transmitting relays of therepeater may be adjusted to line-up signal impulses sent from thatoperating station. However, `signals from any other operating station inthe circuit will be repeated by the transmitting relays with a certaindegree of bias, depending upon the electrical distance between thestations.

Moreover, in cases where there is only one operating station in acircuit, it may be impossible to obtain line-up signals from thisstation. Under such conditions it becomes necessary to center thearmatures of the repeating relays to line-up signals initiated at therepeating station, even though it is realized that signals transmittedfrom the operating station will be biased somewhat to the marking sideas they are repeated by the relays.

The object of my invention is to provide means for so shaping thesignals transmitted at the several operating stations that all signalswill be unbiased as they leave the contacts of the transmitting relaysof the repeater.

In the following description I shall refer to the accompanying drawingwhich is a diagrammatic .illustration of a single current circuit havinga plurality of operating stations and repeating stations.

As is known to engineers, it is characteristic of single currentcircuits that the capacity and/or leakage between the conductor andground causes a distortion of the wave shape of the signals transmittedover the circuit. For example, if the transmitting relays R1 and R2 atthe repeating stations at one end of the circuit are adjusted (ciirs-70) until the armatures are centered for signals from a make andbreak means inserted in the line at the same end of the circuit, therelays will be biased to some degree to the marking side when signalsare transmitted from operating station 5:; No. 1 and will be biased to agreater degree to the marking side when signals are transmitted fromoperating station No. 2.

l Again if the transmitting relays R1 and R2 are centered to signalssent from operatingstation 10.4 No. l, the relays will be biased to somedegree to the spacing side when the signals are sent from the repeatingstations and they will be biased to some degree to the marking side whenthe signals are sent from operating station No. 2. Like- Wise, if thetransmitting relays R1 and Rz are centered to signals from operatingstation No. 2, they will be biased to some degree to the spacing sidewhen the signals are sent from operating station No. l and will bebiased to a greater degree spacing when the signals originate at therepeating stations. The extent of the bias to marking or to spacing asthe case may be, is dependent upon the time constant of the circuit andupon the amount of capacity and/or leakage between the conductor andground.

' In order to overcome the difficulties above mentioned, I provide meansfor shaping the signal impulses at the several operating stations sothat the signals received at one end of the circuit shall correspondwith the signals received from the most distant point. In this mannerthe transmitting relays at the repeating stations located at one end ofthe circuit may be adjusted toI line-up signals from any point in thecircuit and hence the signals from all pointsv are unbiased as theyleave the contacts of the transmitting relays of the repeaters.v

Line jacks J are connected in the line at each station, The transmittersT connected to the plugs at the operating and repeating stations may beof the simplex type or any other suitable make and break signalingdevice. A shaping network comprising a variable condenser C in serieswith a resistance r is connected across the tip and sleeve of the jacksat all but the most distant station. Normally the jack is closed at itscontacts, thereby short-circuiting the network.

The operation of my uniform signal shaping arrangement is asfollowsz--Current being first established on the line from the generatorG, the transmitting relays R1, R2 at the repeaters are centered toline-up signalsl from the most distant station, i. e., operating stationNo. 2. The transmitter T at a repeating `station is then plugged in andidentical signals are sent into the relays. Without changing theadjustments of the transmitting relays, the value of the capacity acrossthe line-up jack is varied until the signals from this point leave therelay unbiased or on center. The value of the capacity across the jackis' then recorded.

Likewise line-up signals are transmitted from the transmitting jack atthe No. 1 operating station. Likewise Without changing the adjustmentsof the transmitting relays, the value of the capacity across thetransmitting jack is varied until the signals from this point leave therelays unbiased or on center. This value of the capacity then remainsfixed across the transmitting jack.

If the characteristics of the single current circuit remain the same asthey Were at the initial line-up tests, it will be found that thetransmitting relays at the repeater will be centered or unbiased tosignals from any station when the condenser vis adjusted tothepredetermined capacity initially determined for that station. Singlecurrent circuits are mainly used to connect stations within the area ofa city and its outlying districts and the conductors are thereforemostly in underground cables so that the circuit is permanentlyestablished except for the removal of the repeaters for use elswherewhen the circuit is not in use.

I claim:-

1. A single current signaling circuit comprising a plurality ofoperating stations located at various points in said circuit and arepeating station, signal transmitting devices at said operatingstations, a repeater embodying a transmitting relay at said repeatingstation having contacts adapted to repeat signals into a trunk line, anda signal shaping network at each station which is connected in shunt tothe corresponding transmitter when said transmitter is inserted in saidcircuit, the electrical constants of each network being so adjusted thatsignals transmitted from each of said stations cause unbiased signals tooperate said relay.

2. A single current signaling circuit comprising a plurality ofoperating stations located at various points in said circuit and areceiving or repeating station, said operating stations being providedwith transmitters, a signal receiving apparatus at the last namedstation having an actuating magnet adapted to be operated by signalsfrom said operating stations and signal shaping means at each stationwhich is connected in shunt to the corresponding transmitter when saidtransmitter is inserted in said circuit, the shaping means at eachstation being so adjusted that signals transmitted from each of saidstations cause unbiased signals. to operate said magnet.

GEORGE G. LIGHT.

